Given that pharmaceuticals and nanomaterials (NMs) used in consumer products such as sunscreens and cosmetics have the same discharge pathways (i.e. down the sink), there is a strong potential for combined effects. This is amplified by the intrinsic tendency of both NMs and pharmaceuticals to interact with their surrounding medium, and the tendency of NMs to bind a “corona” of biomolecules from their surroundings. Thus, there may be a likelihood of interaction between them leading to mixture toxicity and/or enhanced uptake of pharmaceuticals via active transport alongside NMs in the so-called Trojan horse effect.
For this reason, it becomes crucial to understand how this co-existence can affect the transport and fate of both NMs and pharmaceuticals and the toxicity of both categories of contaminants toward indicator organisms. Freshwater microbial communities, such as biofilms, play a vital role as indicator species, as changes in the diversity, structure and function can arise in response to pollution, climate stress or other factors, which can be utilised to monitor ecosystem health. Building on a long track record of assessing interactions of NMs with microbial communities or chemical mixtures, this project will further enhance our knowledge of mixture toxicity by exploring the co-exposure of NMs and pharmaceuticals.
Starting from the concept of the acquired ecological biomolecule corona, the coating of biomolecules acquired by engineered nanomaterials when exposed to a biological medium, the pharmaceutical-containing eco-corona composition is a new and fascinating area of research.
The results from the project will have important policy and regulatory implications, such as for REACH and the Water Framework Directive.
Task 1a focuses on investigating fundamental interactions of surface-functionalised nanomaterials with environmentally relevant media such as different artificial (e.g. OECD, artificial freshwater as well as different natural freshwaters (natural organic matter content, pH, ionic strength and salinity). Physico-chemical characterisation (size distribution, surface charge, surface speciation) of NMs will be carried out with different techniques.
Task 1b will investigate interactions between NMs and extrapolymeric substances (EPS) exuded by microbes. Biomolecules secreted by model single bacterial and algal species will be characterised, as will NM stability therein. Eco-corona formation and its dynamic behaviour will also be analysed.
Task 1c will analyse interactions, i.e. adsorption kinetics, thermodynamic stability and stoichiometry, ligand exchange, between pharmaceuticals and NMs which have been altered by either biomolecules from the abiotic environment such as humic substances or biomolecules exuded by microbes (EPS).
Task 2a will deal with the effects of stress on the formation and composition of extracellular polymer substances (EPS) with the NMs. Selected single microbial species such as green algae and bacteria will used as model systems.
Task 2b will investigate the effects of this changed ‘stressed’ EPS on toxicity of the NMs as well as the mixtures with the pharma-containing eco-coronas. Ecotoxicity tests with the model organisms selected in Task 2a will be performed to study the relative dose-response parameters.
Task 2c will combine data from Tasks 2a and 2b to extrapolate results from model species to more complex and ecologically relevant microbial communities. Validation experiments will be carried out to infer how NMs with different eco-coronas affect the co-transport, bioavailability and toxicity of pharmaceuticals for a representative algal species.
Training and Skills
CENTA students are required to complete 45 days training throughout their PhD including a 10 day placement. In the first year, students will be trained as a single cohort on environmental science, research methods and core skills. Throughout the PhD, training will progress from core skills sets to master classes specific to the student's projects and themes.
The successful candidate will be trained in the characterisation of the acquired eco-corona and will gain advanced skills in the investigation of the interactions between nanomaterials and common organic pollutants such as pharmaceuticals. Specific training in ecotoxicology both single species and community approaches, and a subset of the following novel analytical techniques: single cell and single particle ICP-MS, confocal RAMAN, Quartz Crystal Microbalance and Isothermal Titration Calorimetry.
Year 1: Mastering the basics: culturing single species and biofilms, nanoparticle characterisation and eco-corona assessment.
Year 2: Community responses to nanoparticles, pharmaceuticals and mixtures in various ratios, utilising the ECOlab recirculating streams. Utilisation of the field season (April-October) for exposures and collection of samples for ongoing analysis. Note many parameters have to be measured in situ.
Year 3: Focus on eco-corona, omics and integration of data to assess mixture effects utiliing existing models such as concentration addition and independent action. Writing of papers and thesis.
Partners and collaboration (including CASE)
The project leverages a strong existing collaboration between UoB and CEH, and will align with and benefit from collaboration with the Horizon2020 project NanoFASE (coordinated by CEH). Existing industry partnerships, for example with Perkin Elmer (Single cell SP-ICP-MS) and/or Sciex (Eco-corona) will be expanded through CASE partnerships.
Please contact Iseult Lynch, email@example.com for further details.